Certain agricultural machines, such as balers and forage harvesters, are required to pick up crop material that has been cut but still lies on the ground. The mechanism used to gather the crop material from the ground and feed it into the machine for processing is known as, and herein referred to as, a pickup. A pickup typically comprises a drum rotatably mounted on a frame and having radially projecting spikes to drive the crop material upwards, past a guide (that is termed a windguard) and then into a feed channel through which the crop material is conveyed into the machine for processing.
A known design of windguard comprises a roller extending transversely across the width of the pickup located above and forward of the drum. The windguard is mounted on its opposite ends on two support arms that are pivotable relative to a frame of the pickup so that the gap between the roller and the drum increases as the flow of crop material increases. Instead of a rotating roller, the windguard may comprise a plate or shield to act as a deflector, but a roller is preferred as it offers less resistance to the crop flow.
To guide and contain the crop material after it has passed the windguard, it is known to provide a guide in the form of tines that extend parallel to the direction of crop flow, the tines being mounted on a crossbar secured to the two support arms carrying the windguard. Classically, the crossbar and the tines are secured in such manner that they do not move relative to the support arms of the windguard. This, however, leads to a problem in that as the windguard rises to increase the gap between itself and the drum, the support arms on which it is carried pivot upwards and this in turn alters the inclination of the tines. The inclination of the tines results in a funnel effect that reduces the depth of the crop flow path downstream from the windguard.
EP 1 252 813 addresses this problem by allowing the crossbar on which the tines are mounted to pivot relative to the support arms of the windguard. In one embodiment disclosed in EP 1 252 813, the tines can pivot freely downwards by the action of gravity and upwards by the crop flow. Abutment stops are provided to limit the angular range of movement of the tines. In a second disclosed embodiment, a linkage connected to the crossbar and the frame of the pickup holds the tines firmly so that they cannot move freely but the angular position of the tines relative to the support arms of the windguard varies as the windguard rises and falls.
In the first embodiment of EP 1 252 813, the tines can move in order to accommodate surges in the flow of crop material by allowing a range of free movement of the tines for enlarging the depth of the crop flow path. The lower limit of the crop however still follows the same path of motion as in the design with a secured crossbar and as such in the first embodiment the tines still create the funnel effect which obstructs the flow of the crop and increases the resistance to crop flow.
In the second embodiment of EP 1 252 813, the movement of the tines is linked in a fixed relation to the movement of the support arms and in this way avoids the funnel effect. In this way the funnel effect and the associated flow resistance are reduced, but as they are devoid of a free range of movement they cannot accommodate a sudden surge in the flow quickly and as a result a blockage may still occur.
Therefore there still exists a need for a system that can achieve both effects simultaneously, namely allowing a free range of movement for allowing a quick reaction to a sudden surge of crop material and avoiding the funnel effect.